The inhalation of smoke generated from combustion of tobacco and tobacco substitute is known to be health hazard.
The removal of harmful or potentially harmful constituents from tobacco smoke has been the subject of extensive research efforts. Several methods have been employed to either bind or destroy harmful constituents by passing the tobacco smoke through a treated filter or by incorporating in the tobacco certain substances which are capable of reducing the harmful components in tobacco smoke such as carbon monoxide, hydrogen cyanide, formaldehyde, acrolein, nicotine, phenols, tars, polycyclic hydrocarbons and other toxic components.
There are many procedures which serve the purpose of filtering tobacco smoke. The best commercial cigarette filters, known as "multifilters", basically take advantage of special varieties of materials which adsorb or retain a given portion of the harmful or potentially harmful components of tobacco smoke. For instance, Phillip Morris produces a "multifilter" which consists of a black cellulose acetate base covered with a specified amount and quality of activated charcoal. This section of filter is closed with a white cellulose acetate cover filter at the sucking end of the cigarette (see FIG. 1-A). A filter arrangement shown in FIG. 1-B is also well known, in which two cylinder-shaped filters of either the same or different materials are spaced by 3 to 5 mm apart, the interspace being then filled with adsorbents of granular structure, mostly charcoal or silicates, or mixtures thereof.
A number of substances capable of reducing the harmful components of tobacco smoke have been applied to the cigarette filter. For instance, U.S. Pat. No. 4,753,250 (1988) describes a process for producing cigarette filter comprising L-ascorbic acid (Vitamin C), which is capable of chemically binding formaldehyde in the cigarette smoke,; U.S. Pat. No. 4,414,988 (1983) discloses a tobacco filter containing an aqueous solution of ferric ion binding protoporphyrin ring structure as a removal agent for carcinogenic substances in tobacco smoke; U.S. Pat. No. 3,664,352 (1972) describes a filter containing a water insoluble mixed-metal carbonate of an alkaline earth metal which is capable of removing hydrogen cyanide from tobacco smoke; U.S. Pat. No. 3,943,940 describes a method of removing nicotine by adding potassium permanganate to the cigarette filter; U.S. Pat. No. 3,110,315 (1963) discloses a method of employing tannic acid and its ester to remove nicotine from tobacco smoke. Other methods of making cigarettes with reduced harmful components include adding to the cigarette paper calcium sulfamate (U.S. Pat. No. 3,782,393; 1974), or incorporating a catalytic amount of transition metal compound into the tobacco (U.S. Pat. No. 4,125,118).
In spite of these efforts which have apparently not been adopted successfully in the industry, recently there has been escalating public awareness and governmental concern with respect to the health hazards associated with the cigarette smoking.